##### 3.2.2.4.20 TLS Using ALPN
Confirming the Applicant's control over a FQDN by validating domain control of the FQDN by negotiating a new application layer protocol using the TLS Application-Layer Protocol Negotiation (ALPN) Extension [RFC7301] as defined in RFC 8737. The following are additive requirements to RFC 8737.
The token (as defined in RFC 8737, Section 3) MUST NOT be used for more than 30 days from its creation. The CPS MAY specify a shorter validity period for the token, in which case the CA MUST follow its CPS.
Except for Onion Domain Names, CAs performing validations using this method MUST implement Multi-Perspective Issuance Corroboration as specified in [Section 3.2.2.9](#3229-multi-perspective-issuance-corroboration). To count as corroborating, a Network Perspective MUST observe the same challenge information (i.e. token) as the Primary Network Perspective.
**Note**: Once the FQDN has been validated using this method, the CA MUST NOT issue Certificates for other FQDNs that end with all the labels of the validated FQDN unless the CA performs separate validations for each of those other FQDNs using authorized methods. This method is NOT suitable for validating Wildcard Domain Names.